Update Manager roaming test with promise

gistfile1.js

      test('should handle clicking download when using data connection ' +
            'in the first time',
          function(done) {

        MockNavigatorSettings.mSettings['ril.data.roaming_enabled'] = false;
        var getSpy = this.sinon.spy(UpdateManager, '_getDataRoamingSetting');
        UpdateManager.downloadDialog.dataset.nowifi = true;

        var evt = document.createEvent('MouseEvents');
        evt.initEvent('click', true, true);

        UpdateManager.requestDownloads(evt);

        getSpy.lastCall.returnValue.then(function() {
          var css = UpdateManager.downloadViaDataConnectionDialog.classList;
          var titleL10nId =
            UpdateManager.downloadViaDataConnectionTitle
            .getAttribute('data-l10n-id');
          var messageL10nId =
            UpdateManager.downloadViaDataConnectionMessage
            .getAttribute('data-l10n-id');

          assert.isTrue(css.contains('visible'));
          assert.equal(titleL10nId, 'downloadUpdatesViaDataConnection');
          assert.equal(messageL10nId,
            'downloadUpdatesViaDataConnectionMessage2');
        }).then(done, done);
      });

      test('should handle clicking download when using data ' +
            'connection roaming in the first time',
          function(done) {

        UpdateManager.downloadDialog.dataset.nowifi = true;
        MockNavigatorSettings.mSettings['ril.data.roaming_enabled'] = true;
        var getSpy = this.sinon.spy(UpdateManager, '_getDataRoamingSetting');

        var evt = document.createEvent('MouseEvents');
        evt.initEvent('click', true, true);

        UpdateManager.requestDownloads(evt);

        getSpy.lastCall.returnValue.then(function() {
          var css = UpdateManager.downloadViaDataConnectionDialog.classList;
          var titleL10nId =
            UpdateManager.downloadViaDataConnectionTitle
            .getAttribute('data-l10n-id');
          var messageL10nId =
            UpdateManager.downloadViaDataConnectionMessage
            .getAttribute('data-l10n-id');

          assert.isTrue(css.contains('visible'));
          assert.equal(titleL10nId,
            'downloadUpdatesViaDataRoamingConnection');
          assert.equal(messageL10nId,
            'downloadUpdatesViaDataRoamingConnectionMessage');
        }).then(done, done);
      });